highlight selected item in recyclerview android with code examples

Recycler View is a powerful and flexible tool to display lists in Android. It is the successor of List View and offers improved performance, flexibility, and the ability to handle large data sets with ease. One of the essential features of any list is the selection of items. Highlighting the selected item in Recycler View is an essential aspect of UI design that can enhance user experience. In this article, we will explore how to highlight a selected item in Recycler View and provide code examples to enable you to implement this feature in your Android apps.

What is Recycler View in Android?

Recycler View is a view in Android that provides a flexible and efficient way to display a list of items. It is best suited for large data sets, and its performance outshines the traditional ListView. Recycler View has several advantages over List View:

  1. Efficient memory usage: Recycler View reuses item views rather than creating new views for each item. This efficient memory usage results in faster and smoother scrolling.

  2. Customizable: Recycler View provides more flexibility in the appearance and behavior of items. Developers can create custom layouts for individual items to suit their needs.

  3. Animations: Recycler View has built-in support for item animations, making it easier for developers to add animations to their lists.

  4. Easy Item interaction: The Recycler View provides a built-in mechanism to handle common item interactions such as selection, drag and drop, and swiping.

Now that we understand Recycler View let's delve into the highlight selected item feature.

Highlighting a Selected Item in Recycler View

Highlighting a selected item in Recycler View is purely a visual design aspect that makes it easier for users to identify which item they have selected. Highlighting the selected item also enhances the aesthetic appeal of the UI design. To implement this feature, we will need to use a ViewHolder, an Adapter, and a custom interface to handle item selection.

  1. ViewHolder

The ViewHolder holds a reference to the item view and allows easy access to its individual views.

public class ItemViewHolder extends RecyclerView.ViewHolder {

    private TextView itemName;
    private ImageView itemImage;

    public ItemViewHolder(View itemView) {
        super(itemView);
        itemName = (TextView) itemView.findViewById(R.id.item_name);
        itemImage = (ImageView) itemView.findViewById(R.id.item_image);
    }

    public void bind(final Item item, final ItemAdapter.OnItemClickListener listener) {
        itemName.setText(item.getName());
        itemImage.setImageResource(item.getImage());

        // Set the click listener
        itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                listener.onItemClick(item);
            }
        });
    }
}
  1. Adapter

The Adapter populates the RecyclerView with data and controls the view hierarchy. The ItemAdapter extends RecyclerView.Adapter and creates the UI components for the RecyclerView. In the ItemAdapter, we include a custom interface name OnItemClickListener to handle click events.

public class ItemAdapter extends RecyclerView.Adapter<ItemViewHolder> {

    private List<Item> itemList;
    private OnItemClickListener listener;
    private int selectedPos = RecyclerView.NO_POSITION;

    public interface OnItemClickListener {
        void onItemClick(Item item);
    }

    public ItemAdapter(List<Item> itemList, OnItemClickListener listener) {
        this.itemList = itemList;
        this.listener = listener;
    }
    
    public void setSelected(int position) {
        if (position == RecyclerView.NO_POSITION) {
            return;
        }
        if (selectedPos != position) {
            notifyItemChanged(selectedPos);
            selectedPos = position;
            notifyItemChanged(selectedPos);
        }
    }

    @NonNull
    @Override
    public ItemViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.item_layout, parent, false);
        return new ItemViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ItemViewHolder holder, int position) {
        final Item currentItem = itemList.get(position);
        holder.bind(currentItem, listener);
        if (selectedPos == position) {
            holder.itemView.setBackgroundColor(Color.GREEN);
        } else {
            holder.itemView.setBackgroundColor(Color.TRANSPARENT);
        }
    }

    @Override
    public int getItemCount() {
        return itemList.size();
    }
}
  1. Custom Interface

We create a custom interface to handle click events. Clicking an item triggers the onItemClick method defined in the interface.

public interface OnItemClickListener {
    void onItemClick(Item item);
}

Now we have all the necessary components for the Recycler View list to highlight the selected item. Let's now write the code to achieve this feature.

public class MainActivity extends AppCompatActivity implements ItemAdapter.OnItemClickListener {

    private ItemAdapter itemAdapter;
    private RecyclerView recyclerView;
    private List<Item> itemList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Populate the list with sample data
        initData();

        recyclerView = findViewById(R.id.recycler_view);
        itemAdapter = new ItemAdapter(itemList, this);

        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setAdapter(itemAdapter);
    }

    private void initData() {
        itemList.add(new Item("Item 1", R.drawable.item1));
        itemList.add(new Item("Item 2", R.drawable.item2));
        itemList.add(new Item("Item 3", R.drawable.item3));
    }

    @Override
    public void onItemClick(Item item) {
        itemAdapter.setSelected(itemList.indexOf(item));
    }
}

In the OnItemClick method, we call itemAdapter.setSelected to set the selected item position, which triggers the item selection logic.

Conclusion

In this article, we have explored how to highlight a selected item in Recycler View in Android. We learned that Recycler View is an efficient and flexible tool that provides better performance compared to the traditional ListView. Through the use of a ViewHolder, an Adapter, and a custom interface, we have provided code examples that can enable you to implement this feature in your Android apps. Highlighting the selected item enhances user experience and adds an aesthetic appeal to the UI design.

here is some additional information on the previous topics:

  1. Recycler View in Android:

Recycler View is a powerful tool to display a list of items in Android. It was introduced in Android 5.0 Lollipop and is the successor to ListView. Recycler View is a flexible and efficient way to display large data sets. Its performance is superior to that of ListView due to its ability to recycle views rather than create new ones for each list item. This memory-efficient approach results in smoother scrolling and faster responsiveness. Moreover, Recycler View allows for highly customizable layouts as every item in the list can use its own unique UI component.

Recycler View has several advanced features that make it an indispensable tool in Android development. These features include item animations, drag-and-drop support, swipe-to-dismiss, and built-in item selection. It provides developers with more freedom and flexibility when designing UIs in Android.

  1. ViewHolder:

A ViewHolder is a design pattern used with Recycler View. It is an inner class of the Adapter that holds a reference to the individual view components of an item layout. The ViewHolder pattern is used to increase the performance of Recycler View by avoiding the frequent look-ups of UI components from the layout. It caches the views and provides an efficient way to get references to their UI elements. This approach minimizes the use of the findViewById method, which can be costly and reduce performance.

In simple terms, the ViewHolder is used to decrease the number of calls to findViewById(). It stores the UI elements of a list item that are accessed frequently (such as a TextView or ImageView), so that calls to findViewById can be avoided. Instead, the UI elements can be accessed directly through a Reference that ViewHolder holds.

  1. Adapter:

An Adapter is a bridge that connects data to the UI in Recycler View. It manages the data and creates the list items by inflating the item layout, filling it with the data, and binding it to a ViewHolder. The Adapter is an essential component of Recycler View as it controls the layout of individual items as well as the entire list.

The Adapter provides a template for how the data should be displayed in each item, and it knows how many items are in the list. It exposes methods that allow the list to be updated, such as add, remove, or update. The Adapter also handles events such as item click or long click by calling the appropriate listener (if it exists).

In summary, the Adapter acts as an intermediary layer between the data and the user interface. It manages and presents the data in the Recycler View in a way that is easy to understand and digest.

  1. Custom Interface:

A custom interface is a way to define a callback mechanism to handle events from a user interface component. We use a custom interface in the context of Recycler View to enable the selection of items and trigger specific actions. For example, a custom interface can be used to notify the Adapter that an item has been clicked and needs to be highlighted.

In the previous example, we used a custom interface called OnItemClickListener to handle the click events. We defined a method inside this interface, onItemClick, that we called when an item was clicked. By defining this callback, we delegated the responsibility of handling item clicks to the specific component that implemented the interface.

Overall, using a custom interface is a clean and organized way to pass data between the Adapter and the Activity. It separates the handling of events from the presentation of data, making the code more modular and easier to maintain.

Popular questions

  1. What is Recycler View, and why is it useful in Android?

Recycler View is a powerful tool in Android that provides a flexible and efficient way to display a list of items. It is an improvement over the traditional ListView and offers better performance, customizability, and support for handling large data sets. Recycler View is useful in Android because it enables apps to display large amounts of data in an organized and readable format.

  1. What is a ViewHolder in Recycler View?

A ViewHolder is an inner class of the Adapter in Recycler View that holds a reference to the view components of an item layout. This pattern is used to improve Recycler View performance by avoiding the frequent look-ups of UI components from the layout. The ViewHolder stores the views and provides an efficient way to get references to their UI elements, which minimizes the use of the findViewById method.

  1. What is an Adapter in Recycler View?

An Adapter is a bridge that connects data to the UI in Recycler View. It manages the data and creates the list items by inflating the item layout, filling it with the data, and binding it to a ViewHolder. The Adapter is an essential component of Recycler View as it controls the layout of individual items as well as the entire list.

  1. What is a custom interface, and how is it used in Recycler View?

A custom interface is a way to define a callback mechanism to handle events from a user interface component. In Recycler View, we use a custom interface to enable the selection of items and trigger specific actions. For example, a custom interface can be used to notify the Adapter that an item has been clicked and needs to be highlighted. By defining this callback, we delegated the responsibility of handling item clicks to the specific component that implemented the interface.

  1. How do you highlight a selected item in Recycler View with code examples?

To highlight a selected item in Recycler View, we need to use a ViewHolder, an Adapter, and a custom interface to handle item selection.

Here is an example code snippet to highlight a selected item in Recycler View:

public void onBindViewHolder(@NonNull ItemViewHolder holder, int position) {
    final Item currentItem = itemList.get(position);
    holder.bind(currentItem, listener);
    if (selectedPos == position) {
        holder.itemView.setBackgroundColor(Color.GREEN);
    } else {
        holder.itemView.setBackgroundColor(Color.TRANSPARENT);
    }
}

@Override
public void onItemClick(Item item) {
    itemAdapter.setSelected(itemList.indexOf(item));
}

In the onBindViewHolder method, we check if the current item position is equal to the selected position. If it is, we set the background color of the item view to green; otherwise, we set it to transparent. To set the selected item, we call the itemAdapter.setSelected method in the onItemClick callback defined in the custom interface.

Tag

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As a developer, I have experience in full-stack web application development, and I'm passionate about utilizing innovative design strategies and cutting-edge technologies to develop distributed web applications and services. My areas of interest extend to IoT, Blockchain, Cloud, and Virtualization technologies, and I have a proficiency in building efficient Cloud Native Big Data applications. Throughout my academic projects and industry experiences, I have worked with various programming languages such as Go, Python, Ruby, and Elixir/Erlang. My diverse skillset allows me to approach problems from different angles and implement effective solutions. Above all, I value the opportunity to learn and grow in a dynamic environment. I believe that the eagerness to learn is crucial in developing oneself, and I strive to work with the best in order to bring out the best in myself.
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